Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Unrealized gain (loss) on available-for-sale marketable securities, net of taxes	$ 791	$ 1,416	$ 97	$ (1,138)	$ 2,207	$ (1,041)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from available for sale municipal bonds					7,145	5,775
Unrealized gains related to equity securities	1,600		1,000		5,000
Municipal bonds — available-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from available for sale municipal bonds	3,600		3,300		7,100	5,800
Realized gain	$ 100				$ 100
Realized loss			$ (100)			$ (200)